Photodegradable polyesters prepared from ketonic dicarboxylic acids

ABSTRACT

Condensation polymers such as polyamides, polyesters, polyurethanes, polyepoxides, polyamide esters, polyureas and polyamino-acids which are photodegradable on exposure to U.V. light, due to the presence in the copolymer backbone of units of structure   IN SMALL AMOUNTS

United States Patent [1 1 Guillet et a1.

[4 1 Apr. 15, 1975 PHOTODEGRADABLE POLYESTERS PREPARED FROM KETONIC DICARBOXYLIC ACIDS [76] Inventors: James Edwin Guillet, 31 Sagebrush Ln., Don Mills, Ontario; Ervin Dan, 376 Brunswick Ave., Apt. 502, Toronto 4, Ontario, both of Canada [22] Filed: Apr. 18, 1972 [21] Appl. No.1 245,176

Related U.S. Application Data [63] Continuation-in-part of Ser. No. 135,426, April 19,

1971 abandoned.

3,039,996 6/1962 Ferstandig et a1. 260/63 Primary Examiner-Lester L. Lee Attorney, Agent, or Firm-Robert G. Hirons [57] I ABSTRACT Condensation polymers such as polyamides, polyesters, polyurethanes, polyepoxides, polyamide esters, polyureas and polyamino-acids which are photodegradable on exposure to UV. light, due to the presence in the copolymer backbone of units of structure in small amounts 5 Claims, No Drawings PHOTODEGRADABLEFPOLYESTERS'PREPARED FROM KETONIC DICARBOXYLIC ACIDS CROSS REFERENCE TO RELATED APPLICATION This is a continuation-in-part of US. application Ser. No..l35,426, filedApr. I9. 1971 and now abandoned.

BACKGROUND OF THE INVENTION This invention relates to disposable plastic packaging materials. suchas films. wrappers. cups. bottles. trays, cartons and the like used for packaging perishable commodities such as food, condiments. beverages etc.. and household ,products in general. The invention also relates to plastic compositions suitable for use in such packaging materials. More specifically. it relates to plastic packaging-materials, and plastic compositions for use therein. which when discarded in an outdoor environment will degrade to become part of the soil, or

be washed away by rainfall or wind erosion in a harmless form. H

The increasing use of plastic packaging materials which are then discarded has created serious problems of pollution and litter. Because mose conventional plastic materials used in packaging have long lifetimes in exterior environments the accumulation of litter of these materials in parks and recreational areas, and even in conventional garbage dumps, has led to many environmental and esthetic problems.

Materials which gradually decompose would. of course. solve the litter and pollution problems, provided they decomposed relatively rapidly. Such materials could perhaps be made by including in a packaging plastic an agent which causes the material to decompose. However, against this factor of desirable decomposition must be weighed the requirement that the shelf life of the packaging plastic must be rigidly controlled. and in most cases must be indefinitely long. for proper protection of the perishable contents.

' The present invention provides polymeric packaging materials which degrade under the action ofthe ultraviolet light of the sun. but do not degrade to any appreciable extent otherwise. Thus these polymeric packaging materials start to degrade after they have been descarded in an outdoor environment. but have indefinite storage life indoors. out of contact with direct sunshine.

The wavelengths of light emitted by the sun range from about 2,900A in the ultraviolet to about 20,000A in the infra-red. Only the light with wavelengths ranging from about 4,000 to 8,000A is visible to the human eyeflndoor lighting fixtures emit primarily in this visible range. The present invention is based upon the discovery that there can be introduced into a polymer certain photochemically active chemical groups which do not absorb light of wavelengthin the visible range, but do absorb ultraviolet radiation in the wavelength range from 3.000A to 3.500. Having absorbed radiation, the groups cause scission of the polymer chains, and hence degradation of the polymer. Thus the degradation process is not initiated until the polymer is exposed to the ultraviolet light of the sun. Furthermore, because ordinary window glass absorbsmost of the ultraviolet radiation of the sun, these polymers will not degrade in sunlight which has passed through window glass. Packages or containers made of these materials could be exhibited in store window s,for example, without initiating the degradation process. I

One of the more important classes of plastic materials used for container and packaging purposes are the polyamides such as 6-6 nylon (polyhexamethylene adipamide), 6-12 nylon, polyesters such as polyethylene terephthalate and other polymers coming under the general category of condensation polymers. These polymers break down slowly by photo-oxidation and hydrolysis in an outdoor environment, but molded and extruded objects still retain their shape and an appreciable portion of their original strength for several years under normal weather conditions.

SUMMARY OF THE INVENTION The present invention provides condensation polymers which are substantially totally stable'when exposed to visible light, but which photodegrade on exposure to ultraviolet, i.e., on exposure to direct sunlight. Such polymers are condensation polymers, such as polyamides. polyesters, polyurethanes. etc. containing keto carbonyl groups in side chains, in small amounts.

Thus according to the present invention there is provided a condensation copolymer containing keto'carbonyl groups, said keto carbonyl groups being located in a side chain at a position immediately adjacent to the main polymeric chain, the amount of said keto carbonyl groups. This amount is from about 0.01 weight to about 3 weight, based on the total copolymer sufficient to cause accelerated photodegradation of the condensation polymer to a brittle or friable condition on exposure to ultraviolet light. The other basic desirable properties of well-known polyamide, polyester, and the like condensation polymers are not. however, substantially changed.

THE PREFERRED EMBODIMENTS According to the preferred embodiments of the invention. the structure in the main polymeric chain contains units of the form:-

wherein R is an alkyl, aryl, alkaryl or alkenyl group of from 1 12 carbon atoms and preferably from 1 2 carbon atoms, and R is hydrogen or an alkyl group of from 1 to 6 carbon atoms. When the keto carbonyl group is adjacent to the main polymeric chain or backbone, the rate of photodegradation of the polymer is faster than when the keto carbonyl group forms part of the main polymeric chain or backbone.

0 Such groups may be included in the polymer by including certain comonomers in the polymerization step or by subsequent reaction with the preformed polymer. The simplest procedure is to prepare the copolymer with a suitable amount of a'difunctional. condensable ymonomer such as a dibasic acid of the general structure:

where m is an integer from -6, suitably from 1-6, preferably from 2-4, and n is an integer from 1-6 and preferably 2-4, and R and R are as previously defined, or a glycol of the structure:

where T is selected from the group consisting of methylene chains having 0-6 carbon atoms, and methylene chains of 2-6 carbon atoms interrupted by ester linkages, and Q is selected from the group consisting of methylene chains having 1-6 carbon atoms, and methylene chains of 2-6 carbon atoms interrupted by ester linkages, and R and R are as defined previously. Thus, the keto group may be derived from a monomer of general formula:

2 (CH (CH2) Y where Y and Z are functional groups capable of condensation copolymerization, independently selected from among hydroxyl, carboxylic acid and functional derivatives thereof. whic include acid halides, esters, salts and the like, amine, amine salts, isocyanates, epoxies and the like.

The inclusion of the ketone group in the polymer chain permits the absorption of ultraviolet light in the range from 3000 A 3400 A, and in solution all copolymers containing this ketone linkage adjacent to the chain will degrade quite rapidly when exposed to U.V. light. The degradation occurs as a result of scission of the main chain of the polymer at the carbon atom adjacent to the carbonyl, and usually results in the formation of a double bond.

Examples of suitable acids useful as monomers to incorporate the aforementioned structural unit are keto substituted derivatives of straight chain a,w-dibasic ali phatic acids such as adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid. It is preferred that the acid, used have at least 2 carbon atoms between the carboxyl groups therein, and that the oxygen of the ketone substituent group be attached to carbon atoms other than a carbon atom at position a to a carboxyl group. Otherwise, is the resultant condensation polymer, the ketone carbonyl will be in such close proximity to an ester or amido carbonyl group that its absorption will be affected. lt will tend to absorb radiation, and hence cause degradation of the polymer, at wavelengths in the visible region.

It is to be understood that, when the specification refers to acids, functional derivatives which perform in the same manner as acids, such as acid halides, esters, salts and the like, are also included.

Among the most preferred is y-acetyl pimelic acid, of formula:

Hooc.cH -cn -t:H-ca -cr1 -co.oH

However, many other similar materials can be used, such as y-benzoyl pimelic acid and functional derivatives thereof, 'y-acetyl suberic acid, S-acetyl azelaic acid and the like.

Such keto substituted acids and functional derivatives thereof, and methods for their preparation, are known in the art. See for example U.S. Pat. No. 2,438,961, Albert B. Boese, issued Apr. 6, 1948. cording to this method a diacyl-a,w-dicyanogen is hydrolysed to the corresponding cam-diacid, with the concurrent loss of one acetyl group, to give a 'keto substituted diacid as hereinbefore defined. A further method is described in U.S. Pat. No. 2,342,606, Herman A. Bruson, issued Feb. 22, 1944. This method prepares the keto substituted dibasic acids by hydrolysis of the corresponding keto-substituted a,w-di nitrile compounds.

The diamines which can be used can have generally.

similar structures to the above diacids. Preferably the oxygen of the ketonic group is attached to a carbon atom which is no closer than 62 to either amino group, so as to avoid the possible interference of the amide linkages with the absorption spectrum of the ketone side chain groups. Suitable examples of such diamines are 'y-acetyl-pentamethylene-q:,w-diamine and y-acetylhexamethylene-a,w-diamine.

Such keto substituted diamines and methods for their preparation are known in the art. For example they may be prepared by mild reduction'bf the corresponding a,mdinitrile compounds referred to previously, according to the method of Wily and Adkins, Journal of the American Chemical Society, Vol 60, page 914 (1938). As an alternative they can be prepared from the corresponding dibasic acids previously referred to, by the method of Wallis et a1, Organic Reactions,

Vol 3, page 267. or by the method of Smith, Organic Reactions", Vol 3, page 337.

The glycols which can be used have similar structural requirements to the diacids and diamines described above. Once again, it is preferred that the oxygen of the ketonic group is attached to a carbon atom which is not closer than B to either hydroxyl group. Suitable examples of such glycols are y-acetyl-pentatnethylene-mwglycol and y-acetyl-hexamethylene-oz, w-gl ycol.

Such glycols (or diols) and methods for their preparation are known in the art. They can be prepared by an aldol condensation reaction, as described in British Pat. Specification No. 922,975, for example.

It will of course be understood that it is not necessary to use both a ketone-substituted acid and a ketonesubstituted amine in preparing the polyamides of this invention. Only one of the monomers need contain carbonyl groups. The requirement is that the product must contain some keto-carbonyl side chain groups in an amount sufficient to cause photodegradation. It is thus unimportant whether the groups are derived from the amine, acid or both. similarly in preparing polyesters of the present invention, the keto groups can be derived from either or both monomers. In a further embodiment, amino acids can be copolymerized with the ketocontaining'monomer. In this category of amino acids, there are included the lactams such as caprolactam, valerotactam, and butyrolactam.

A further type of condensation cbpolymer in accordance with the present invention is a polyurethane, in

which one of the monomers, either a diol or a diisocyanate, contains the aforementioned keto carbonyl I group.

Fri-

within its polymeric structure. For the most rapid photodegradation on exposure to ultraviolet radiation, the copolyamide should have a glass transition temperature Tg lower than ambient temperature, that is less than about 30C. The reason for this is as follows:- It has been discovered that the chain scission process initiated by the absorption of-light by the carbonyl group adjacent to the copolyamide chain is only effective if there is sufficient mobility in the molecule to form a transient intermediate or excited state. At temperatures below the glass transition temperature the mobility of thepolymer chains is low. It has been found experimentally that the efficiency of the photochemical scission process in the solid polymer is greatly reduced at such temperatures. It therefore takes a much longer time to degradethe polymer at temperatures below Tg than it does above Tg. Thus if his required that the plastic material degrade relatively rapidly, i.e., over a period of a few weeks, when discarded under ordinary environmental conditions, the glass transition temperature of the material should be less than the ambient temperature at which the object will be exposed to the suns radiation. This temperature may of couse vary somewhat depending on the climate of the locality in which the material is to be used, being much higher in tropical regions than in the arctic. However, for temperate climates a material having a glass transition less than about 20-30C is desirable.

Methods of controlling the glass transition temperature of a copolyamide are well known. For example, one may reduce the glass transition temperature, Tg, by the addition of a plasticizer, although these are not commonly used for polyamides. Careful selection of suitable monomers is preferred for controlling Tg. The use of a branched chain diacid or diamine as one of the comonomers in the copolyamide tends to reduce both the melting point and the glass transition temperature. This method is to be preferred in the invention, since the groups so introduced will not in general affectthe photochemistry of the system, and as they form part of the polymer system they will not migrate or be extractable.

Also, in order to have physical properties appropriate to form films or molded objects with sufficient strength and stiffness to be used as packaging material, the eopolyamides should be crystalline, and have a melting point exceeding about -l00C. I

The requirements that the glass transition temperature Tg should be lower than about 20C is appropriate for materials that are to photodegrade relatively rapidly. However, materials which photodegrade more slowly, over periods of 1 year or so, are also useful in many applications, and certainly provide improvements over conventional plastics materials as regards litter and disposal problems. Such materials do not need to have such low Tg, and are within the broad scope of this invention.

In order to achieve the maximum effect it is desirable that the ketone groups be distributed throughout the entire polymer chain and preferably at maximum distance from each other. Further, most of the polymer should preferably contain some ketonic groups, otherwise some of the polymer may not degrade photochemically. These conditions can usually be met by employing suitable control of the reaction conditions.

Polyamide ester condensation polymers, polyureas and polyepoxides are further examples of materials which can be made photodegradable in accordance with the invention, using suitable keto containing monomers.

As will be clear from the foregoing, the process and compositions which can be used in the practice of our invention are not restricted to binary copolymers but will also apply to multi-component condensation copolymers with a variety of dibasic acids, diamines, glycols, or isocyanates. Polyamide esters are examples of such copolymers being derived from diacids, diamines and glycols, in the correct proportions.

The dibasic acids, diamines, glycols and diisocyanates used in combination with the monomers containing keto carbonyl groups in preparing the copolymers of the invention may be any of those known to be useful in condensation reactions.

Useful dibasic acids may be defined by the general formula HOOC R COOH where R is a divalent hydrocarbon radical which may be aliphatic, alicyclic,

aromatic or araliphatic radicals, substituted or unsubstituted. Representative examples of such dibasic acids acid Useful diamines may be defined by the general formula H N R NH; where R is a divalent hydrocarbon radical selected from the group consisting of ali-,

phatic, alicyclic, aromatic and araliphatic radicals, substituted or unsubstituted. Representative examples of such diamincs are:

dimethylenediamine trimethylenediamine tetramethylenediamine pentamethylenediamine hexamethylenediamine l,2-diaminopropane benzidine (4,4'-diaminobiphenyl) Ortho-tolidine Ortho-phenylenediamine Meta-phenylenediamine Para-phenylenediamine 2,2'-diaminol ,l '-dinaphthyl Para-xylylene diamine Octamethylene diamine Heptamethylene diamine Nonamethylene diamine Decamethylene diamine Undecamethylene diamine Dodecamethylene diamine l,4-cyclohexanc diamine Useful glycols may be defined by the general formula HO R OH where R* is an organic radical selected from the group consisting of aliphatic, aromatic, alicyclic and araliphatic hydrocarbon radicals, substituted or unsubstituted, polyether radicals, and polyester radicals. Hydrocarbon glycols, particularly alkyleene glycols. are preferred, for most condensation copolymers. In the preparation of polyurethanes, however, polyols are among the preferred hydroxyl compounds, especially polyester and polyether glycols and polyols. Representative examples of suitable glycols and polyols are:

ethylene glycol polyethylene glycol propylene glycol polypropylene glycol butanediols pentanediols hexanediols higher alkanediols bisphenols l,4-cyclohexane dimethanol polyester glycols and polyols polyether glycols and polyols Useful diisocyanates may be defined by the general formula:

OCN R NCO where R is a divalent hydrocarbon radical consisting of aliphatic, aromatic, alicyelic and araliphatic. Representative examples of such monomers are:

tolylene diisocyanates diphenylmethane-4,4'-diisocyanate polymethylene polyphenyl isocyanate p.phenylene diisocyanate mesyl diisocyanate 4,4-dicyclohexyl methane diisocyanate xylylene diisocyanates methyl cyclohexyl diisocyanates isophorone diisocyanate Useful diepoxides may be defined by the general formula:

CH CH HC-CH-R where R represents a divalent hydrocarbon or polyether group. I

The amount of ketone carbonyl included in the polymer is preferably within the range 0.01 3 weight percent, based upon the total of polymeric materials. The amount will usually be determined by the rate and extent of degradation required, and as previously discussed the glass'transiton temperature of the material. Higher concentrations of keto carbonyl lead to faster degradation rates up to a limit determined by the thickness of the object to be fabricated from the plastic. If too much carbonyl is included only the surface layers will absorb the U.V. light and in the absence of some means of removing these surface layers and their photodegradation products, very little degradation will occur in the bulk of the material. The optimum concentration can be calculated for a given specimen thickness using the Beer-Lambert Law of photochemistry. For this reason. polymers to be extruded as thin films may contain higher carbonyl concentrations than those used in the manufacture of thicker sections such asl in bottles or waste containers.

At keto carbonyl amounts less than about 0.01 weight percent based on the total copolymer, the accelerated rate of photodegradation is hardly practically significant. Amounts more than about 3 weight per cent show little practical advantage. Further, if the amount is increased above this figure, the condensation eopolymer has to contain such large amounts of the keto-containing monomer that the basic, desirable physical properties of the condensation copolymers, which are well known and around which their extensive applications have been developed, are affected. This is undesirable. It is desired to preserve the basic properties of well established polyamides, polyesters and the like. To obtain such small amounts of keto carbonyl, it is in most cases necessary to use at least 2 other eondensation copolymerizable monomers in addition to that containing the keto group. Thisis usually necessary in order to provide substantially equivalent amounts of eondensable chemical groups in the copolymertzation recipe.

In summary, therefore, the present invention in genera] has the following features:

TABLE Thickness] I00 mil (based on U.V. data Washington DC. average) 50 mil 10 mil 5 Quantum Yield 2 mm l mm 0.2 mm 0.1 0.02

d =0.2 2 months i month 6 da 5 fi 2 s 1 a.

. l0 2 m th figs) 40 20 4 I, S g l? g H.000! 34 years 17 years 3.2 years l.6 years 33 months i. A condensation polymer is synthesized by any of the well known methods of preparing such poly mers, to contain a group of the general structure:

2. The molecular weight of the copolymer should be such that good physical properties may be obtained in molded or extruded objects, and preferably crystalline materials with melting point above 90C and Tg below about 20C are prepared.

3. The copolymeric resin so produced is used to prepare plastic films, blown bottles or molded containers, by any of the usual processes for fabricating thermoplastic materials.

4. These plastic films and containers are used to package various items such as foods, beverages, condiments, medicines salves, etc, and after use the packages can be discarded.out of doors.

The advantage of the compositions of this invention are that when so used, the packaging materials will decompose when exposed to the ultraviolet radiation of the sun, and will shortly break up under the action of wind. rain and other forms of natural erosion. In this form they are susceptible to attack by microorganisms to become part of the natural soil.

The rate at which plastic films or molded pieces degrade in the presence of ultraviolet light can be determined in the laboratory using a mercury vapor arc and filter system. The apparatus consists of a 250 watt medium pressure mercury lamp (A.E.l. type ME/D), with a quartz lens which focusses the light from the lamp into a parallel beam. A solution filter is used to eliminate the visible and infra-red radiation and an interference filter isolates the mercury line at 3130A. This light then impinges on the plastic film or molded object which is held in a metal frame in a metal block thermostatted to maintain its temperature at C. The intensity of the light is monitored with a photocell behind the plastic specimen. The response of the photocell is calibrated using a uranyl oxalate actinometer. To determine the amount of light absorbed, the intensity of the lamp is measured before and after each exposure using the photocell. The intensity of the light passing through the plastic can also be measured during exposure. The lamp intensity depends on various factors such as the voltage supplied, the age of the lamp, and the characteristics of the filters used. In a typical experiment, an exposure of 24 hours in the lamp system is equivalent to the amount of U.V. radiation received in the same area ofa plastic sample in an average summer month.

The efficiency and rate of photodegradation is determined by measuring the number average molecular weight of the specimen before and after irradiation. Thequantity [(M,,) l/M,,] is the number of bonds broken per original polymer molecule in the specimen. Usually 5 to 10 breaks are sufficient, with a polymer of initial molecular weight 50,000 100,000 to render the material brittle and friable so that it will break up under the action of normal erosion processes. This corresponds to an approximate ketone carbonyl content the polymer of from about 0.2 to 0.6 weight per cent. The efficiency of the process is the total number of main chain bonds broker per quantum of light absorbed. This is called the quantum yield 4), and ranges from about 0.003 to unity depending on the structure of the polymer and other factors. The large the value of (b, the more rapid is the degradation process.

The relation between the quantum yield d) and the rate of degradation for specimens of various thickness is given in Table 5. These data are calculated assuming a ketone absorption spectrum similar to that of diethyl ketone and an average intensity of U.V. light of 1.14 X l0- einsteins per square cm per year. This is estimated to be the amount available in normal sunlight on a plane surface in Washington DC. in a normal year. This will obviously change depending on geographic location, but is sufficient to give an idea of the way in which the degradation can be controlled.

The copolymers of the invention can be prepared by any of the conventional means of condensation polymerization. They may be prepared in batch autoclaves, or as is more common in industrial practice, in continuous stirred reactors. Small amounts of antioxidants and other additives may be present during polymerization or added later. They may be processed in conventional molding, extruding, blow-molding or other fabrication processes. They may be used as injection molded objects such as containers, or as extruded films or blown bottles.

The invention is illustrated but not limited by the following examples:

EXAMPLE 1 riod. After 2 minutes stirring ml of 3 percent aqueous hydrochloric acid was added to stop the polymerization. The polymer was then filtered on a sintered glass filter and washed with water until free of salt. The polymer was dried three hours in air at 80C. The yield was 4.3 g of polymer having an inherent viscosity in mcresol of 1.4. It had a glass transition temperature Tg of 55C as measured by a Perkin Elmer Differential Scanning Calorimeter.

EXAMPLE 2 EXAMPLE 3 I The procedure ofExample l was repeated except that 3130 g adipyl chloride and 0.46 g of 'y-aeetyl pimelic acid chloride were used with the diamine. This represents about 1 weight percent keto carbonyl. based on total polymer. 5.2 g of polymer were obtained with an intrinsic viscosity of 1.45. A molded film of this polymer showed a small but finite absorbance in the infra-red, characteristic of the ketone carbonyl.

EXAMPLE The procedure of Example 1 was repeated except that the acid chloride used consisted of a mixture of 0.46 g of y-acctyl pimelic acid chloride and 4.0 g of 3 methyl adipyl chloride. This represents about 1 weight percent keto carbonyl. based on total polymer. The yield of polymer was 6.3 g, having an inherent viscosity of 1.52 and showed evidence of ketone groups by infrared absorption of the solid film.

EXAMPLE 5 The procedure of Example 1 was repeated except that the acid chloride used consisted of a mixture of 0.92 g of y-acetyl pimelic acid chloride and 3.80 g of sebacyl chloride. This represents about 2 weight percent of keto carbonyl based on total polymer. The yield of polymer was 6.8 g having an inherent viscosity of 1.73 and showed evidence of ketone groups by infrared absorption.

EXAMPLE 6 The procedure of Example 1 was repeated except that the acid chloride used consisted of a mixture of 1.02 g of y benzoyl pimelic acid chloride and 3.80g of sebacyl chloride. This represents about 2 weight per cent of keto carbonyl. based on total polymer. The yield of polymer was 7.2 g having an inherent viscosity of 1.43 and showed evidence of ketone groups by infrared absorption spectroscopy.

EXAMPLE 7 Films were pressed from the copolyamides whose preparation is described in Examples i=6 using a Car= ver Press at a temperature of 270C and a pressure of 24.000 p.s.i. The films were tough and transparent and ranged in thickness from 3 to 5 thousandths of an inch.

The melting point T,,, was determined for the film using a hot stage microscope, and the glass transition T determined using a Perkin-Elmer differential scanning calorimeter. The film was then exposed to the ultra violet light source described previously for various lengths of time and tested for brittleness. Brittleness was designated as fracture when the sample was bent through a right angle. The time required for the sample to become brittle was recorded. Previous calibration of the light source indicated that 20 hours exposure corre spond to approximately one month of summer sunshine.

The results obtained are tabulated below:

The procedure of Example 1 was repeated except that 2.09 g of hexamethylene diamine and 0.23 g 1.1 diaminomethyl acetone (3 amino methyl 4 amino 2 butanone) was used with the 3.70 g adipyl chloride. This represents about 1.2 percent wt keto carbonyl group based on the total polymer. 5.0 g of polymer were obtained with an intrinsic viscosity of 0.52. A film of the polymer was cast from formic acid (0.3 mm) and was irradiated in the U.V. Accelerometer. The effect of the irradiation on the molecular weight of the polymer as measured by viscosity is given below:

unirradiated I after 72 hrs irradiation EXAMPLE 9 a. Preparation of Nylon Salt in a 250 ml Erlenmeyer flask was placed 13.14 g adipic acid and 2.16 g ymethyl-yacetyl pimelic acid (prepared by hydrolysis of dicyanoethylated methyl ethyl ketone as per the method of H. A. Bruson. US. Pat. No. 2,343,606) were dissolved in chloroform with gentle heating and then cooled to about 30C. A solu tion of 11.83 g of hexamethylene diamine in chloro= form was added quantitatively to the acid solution. Crystallization occurred almost immediately. The salt was filtered and washed with chloroform and air dried. Yield was 25.1 gms E 93 percent. A 1 percent aqueous solution of the salt had a pH of 6.9. b. Preparation of the Copolyamide 1.5 g of the salt was charged into a polymer tube and after several vacuum N purge cycles the tube was sealed off under vacuum. The tube was placed in a steel tube and placed in a solvent bath of boiling tetrahydro= naphthalene (206C) for 2% hrs. The sealed polymer tube was opened and the polymer transferred to a melt polymerization tube and the polymerization continued using the method quoted in Preparative Methods of Polymer Chemistry". 2nd ed by W. R. Sorens'on and W. Campbell. J. Wiley and Sons. N.Y.. 1968. p.75. The

copolymer has about 1 percent by weight carbonyl group. The polymer was reprecipitated from formic acid by water. A slightly opaquegfilm was cast from formic acid solution which was 0.3 mm thick. This was irradiated in a U.V. Accelerometer (American Ultraviolet Co., New Jersey, U.S.A.) for 96 hrs. The change in inherent viscosity (formic acid 1 percent) is given below:

Initial viscosity before irradiation after 96 hrs irradiation EXAMPLE A mixture of 9.99 g of tetramethylene glycol (1,4- butanediol), 20.70 g of dimethyl sebacate, 2.30 g diethyl butyryl succinate, 0.1 g litharge, and 0.2 g ditertiary butyl hydroquinone was placed in a polymer tube having a side arm and nitrogen capillary inlet reaching to the bottom of the tube. The reaction was heated at about 176C in a vapor bath (p-cymene) for 2 hrs at atmospheric pressure in a current of nitrogen. Then the pressure was slowly reduced over a 4 hr period to 0.05 mm. The temperature was then raised to 215C (naphthalene used in vapor bath) for 4 hrs at the same pressure. The reaction was heated overnight. The polymer which was allowed to cool under nitrogen was a pale yellow solid which was dissolved in chloroform and decolorized with Norite.

The copolymer recovered by precipitation from methanol weighed 20.08 g with an intrinsic viscosity of 0.21. This copolymer is referred to as poly-(TMS-co- EBS). and contains about 1 weight percent ketone carbonyl.

The U.V. spectra of the copolymer showed a characteristic carbonyl absorption band with a peak at 290mg.

the copolymer was soluble in the common organic solvents such as ethyl acetate, chloroform, etc.

The copolymer was dissolved in ethyl acetate and irradiated under the same conditions as in Example 8. The results are tabulated below.

Photodegradation of poly(TMS-co-EBS) at C Based on these results the quantum yield of chain breaking was 5.9 X 10".

EXAMPLE 11 The method used was the same as described in Example 8 (above). The quantities of reactants used were as follows:

butane 1.4 diol 391 gms 1,1 dimethylol acetone 1.18 gms dimethyl sebacate 23.00 gms EXAMPLE 12 The method used was the same as described in Example 8. The quantities of reactants used were as follows:

L4 butane diol 9.90 gms dimethyl sebacate 20.70 gms diethyl 'y acetyl pimelate 2.58 gms (prepared by the method of A'. Boise, U.S.P. 2.437.906

This polymer was off-white and called poly(TMS-co- DEAP).

EXAMPLE 13 The polymers referred to in Examples 11 and 12 were pressed into films 0.25 mm thick and irradiated in the U.V. Accelerometer for 48 hrs. Their initial and final intrinsic viscosities (as a measure of molecular weight) are given below.

7] CHCIII initial final Example ll poly(TMS-co-DMAS) 0.77 0.54 Example l2 poly(TMS-co-DEAP) 0.59 0.40

EXAMPLE 14 An ester diol from ethylene glycol and 3,3 (dicyano ethyl) pentane 2,4 dione was prepared following the method of A. Boese US. Pat. No. 2,437,906 using a 15 fold molar excess of ethylene glycol. The product of esterification was:

which was purified by washing through an alumina column to give a viscous liquid. Preparation of the urethane copolymer 24.08 gms of toluene diisocyanate (Nocconate were dissolved in 50 ml of methyl isobutyl ketone and placed in a three necked, round bottomed flask fitted with a stirrer and protected from moisture. 7.72 gms of ethylene glycol and 4.46 gms of the ester diol in 50 ml of dimethyl sulphoxide was added with rapid stirring and the mixture heated to 120C and kept at that temperature for 2 hrs. After cooling, the solution was diluted with mls of methanol and poured into water in a blender. The polymer was washed with water and then reprecipitated from dimethyl sulphoxide solution with water and after further washing dried in a vacuum oven at 60C.

The powder had an intrinsic viscosity of 0.15 in dimethyl sulphoxide and after 60 hrs irradiation in U.V. Accelerometer the intrinsic viscosity was 0.12.

EXAMPLE l Into a three necked round bottomed flask fitted with a stirrer, a distilling receiver and condenser and a thermometer and a means for removing oxygen, is placed 58 gm hexamethylene diamine. 45 gm butanediol. 182 gm sebacic acid, 43.2 gm methyl yacetyl pimelic acid and 150 ml xylene. The slurry is heated to reflux and the water of condensation was removed via the distilling receiver. As the evolution of water decreases, the xylene was also removed until approximately 40 mls remained. The temperature of the mixture was at this time about 230C. The condensation was run a further 8 hours. Finally the flask was cooled to 100C, the viscous solution thinned with xylene and poured into methanol to precipitate the polymer. This polymer had a ketone carbonyl content of about 1 percent by wt. It had an intrinsic viscosity of 0.4 (dimethyl formamide). After irradiation of a 0.25 mm pressed film 40 hours in a U.V. Accelerometer the intrinsic viscosity in DMF had dropped to 0.28 indicating a substantial decrease in molecular weight.

EXAMPLE l6 An ice cold solution of 17.4 gm toluene diisocyanate in 100 ml of toluene was added with stirring to a cold solution of 10.4 gm hexamethylene diamine 1.2 gm 1,1 diamino methyl acetone in 300 ml N l-lCl solution. To this mixture was added slowly (keeping the flask cold) 300 ml N NaOH solution during the addition the polymer precipitated. The polymer was filtered, washed, and dried. The polymer had an intrinsic viscosity (DMF) of 1.2 and was cast as a 0.40 mm thick film from DMF.

This film was subjected to light in a U.V. accelerometer for 40 hrs after which intrinsic viscosity of the resultant polymer was 0.35.

EXAMPLE 17 a. Preparation of 5 acetyl 5 methyl hexahydro[2- H.Azepin-2-one] (y acetyl 7 methyl caprolactam )(Formula 1 below) y acetyl y (y pimelic acid prepared as described in Example 9 was added to a flask with acetic anhydride in the presence of a small amount of potassium acetate and the mixture refluxed for 6 hrs to produce a polyanhydride. The acetic acid and acetic anhydride were distilled off and the residue heated under reduced pressure 10-15 mm Hg) to pyrolyse the polyanhydride. A pale yellow oil distilling between 140 and 145C at 12 mm was collected. This was found to be a )0:8 mixture of 11 and 111.

On hydrolysis in aqueous acid conditions compound 11 was converted to I.

Upon reaction with hydroxylamine compound 1 gave a solid monoxime which dissolved in sulphuric acid and which on heating gave the rearranged product I which was extracted with methylene chloride after neutralization to give a solid whose infra-red spectrum is consistent with the structure 1 O CH3 b. Polymer 24 gm ofe caprolactam 1.05 gm 7 acetyl 7 methyl e caprolactam prepared as above was placed in a polymer tube having a nitrogen capillary inlet and the caprolactam were melted at C. To the melt was added 0.013 gms sodium as a dispersion in xylene. The tube was transferred to a vapour bath of boiling diphenyl ether and allowed to remain there 10 minutes. The polymer was cooled and broken out of the polymer tube. A film was cast from formic acid (0.3 mm) and irradiated on the U.V. Accelerometer for 40 hours. The effect of the irradiation on the intrinsic viscosity of the polymer is given below:

[1;] in formic acid initial 1.3 after 40 hrs irradiation 0.5

EXAMPLE 18 of 1,1 diaminomethyl acetone in 1 ml of methyl eellusolve acetate and stirred. The solution was sprayed onto a tin plate panel. After most of the solvent had evaporated in air the plate was heated at 100C for /2 hr. A hard film coating was achieved. This coating was denoted composition A. To a similar solution of 10 gms Epon 828 was added 0.5 gm of hexamethylene diamine in 1 ml of methyl cellusolve acetate and stirred. This solution was also sprayed onto a tin plate and baked for V2 hr. at 100C to produce a hard film. This was denoted Composition B. After exposure to 72 hrs of U.V. radiation in a U.V. accelerometer and 48 hrs in a salt fog spray significant rusting had occurred on composition A whilst the composition B and the unexposed portion of coating A and tinplate was not affected by the salt fog spray. This indicates that the integrity of the film had been impaired by the photolysis of the cross linking agent.

Into a four necked flask fitted with a stirrer, a distilling receiver and condenser, a thermometer and .a nitrogen purge inlet was placed the 300 gm xylene. When the xylene had been heated to approximately 100C the rest of the ingredients were charged. The slurry was heated to reflux and the water of condensation collected. As the polymerization proceeded the xylene was removed until 50 gm approximately remained. At this point, the temperature was 215C. The condensation was continued until 80 ml of water had been collected.

The flask was then cooled and diluted with methyl cellosolve acetate to 55 percent solid solution. To 250 mls of this solution, 20 gm of cymel 301 (a methylolated metalume) was added and thoroughly mixed. This solution was sprayed onto tin plate panels and baked mins at 350F to produce a tough film.

After exposure to ultraviolet radiation for 72 hrs and salt fog spray for 48 hours, the panels showed evidence of rusting.

EXAMPLE Using the procedure and materials of Example 19 but with the replacement of 40.4 gm of y Me y acetyl pimelic acid by 29.6 gm adipic acid, a resin was synthesized, blended with methylolated melamine and sprayed onto tin plate.

After exposure to the UV. weathermometer for 72 hrs and salt fog spray for 48 hrs, no damage to the pancls was observed.

What we claim as our invention is:

l. A condensation copolymer obtained by reacting together at least one dibasic acid of formula HOOC R COOH or a functional derivative thereof selected from the group consisting of acid halides, esters and salts which react in the same way as acids, where R is a divalent hydrocarbon radical selected from the group consisting of aliphatic, alicyclic, aromatic and araliphatic. at least one glycol of formula HO R OH where R is an organic radical selected from the group consisting of aliphatic, alicyclic, aromatic and araliphatic hydrocarbon radicals, or a polyether or polyester glycol or polyol and a monomer of the formula B:

where T is selected from the group consisting of methylene chains having 0 6 carbon atoms, and methylene chains of 2 6 carbon atoms interrupted by ester linkages, Q is selected from the group consisting of methylene chains having 1 6 carbon atoms and methylene chains of 2 6 carbon atoms interrupted by ester linkages, R is hydrogen or an alkyl group of l 6 carbon atoms, R is an alkyl, aryl, alkaryl or alkenyl group of from 1 l2 carbon atoms and-X is selected from OH, COOH and functional derivatives thereof selected from the group consisting of acid halides, esters and salts which react in the same manner as acids. the monomer of formula B providing a unit of structure in the backbone of the copolymer, the number of said units in the backbone chain being sufficient to provide from about 0.01 weight percent to about 3 weight percent of ketone carbonyl based upon the total copolymer.

2. A condensation copolymer as claimed in claim 1 wherein the monomer of formula B is a dibasic acid or an aforesaid functional derivative thereof and T and Q are methylene groups.

3. A condensation copolymer as claimed in claim 2 wherein the monomer of formula b is 'y acetyl pimelic acid or an aforesaid functional derivative thereof.

4. A condensation copolymer as claimed in claim 1 wherein the monomer of formula B is a glycol.

5. A condensation copolymer as claimed in claim 2 wherein the glycol of formula HO R OH is a straight chain alkylekne alglyckol. l 

1. A CONDENSATION COPOLYMER OBTAINED BY REACTING TOGETHER AT LEAST ONE DIBASIC ACID OF FORMULA HOOC - R1 - COOH OR A FUNCTIONAL DERIVATIVE THEREOF SELECTED FROM THE GROUP CONSISTING OF ACID HALIDES, ESTERS AND SALTS WHICH REACT IN THE SAME WAY AS ACIDS, WHERE R1 IS A DIVALEENT HYDRCARBON RADICAL SELECTED FROM THE GROUP CONSISTING OF ALIPHATIC, ALICYCLIC, AROMATIC AND ARALIPHATIC, AT LEAST ONE GLYCOL OF FORMULA HO - R4 - OH WHERE R4 IS AN ORGANIC RADICAL SELECTED FROM THE GROUP CONSISTING OF ALIPHTIC, ALICYCLIC, AROMATIC AND ARALIPHATIC HYDROCARBON RADICALS, OR A POLYETHER OR POLYESTER GLYCOL OR POLYOL AND A MONOMER OF THE FORMULA B:
 2. A condensation copolymer as claimed in claim 1 wherein the monomer of formula B is a dibasic acid or an aforesaid functional derivative thereof and T and Q are methylene groups.
 3. A condensation copolymer as claimed in claim 2 wherein the monomer of formula b is gamma - acetyl pimelic acid or an aforesaid functional derivative thereof.
 4. A condensation copolymer as claimed in claim 1 wherein the monomer of formula B is a glycol.
 5. A condensation copolymer as claimed in claim 2 wherein the glycol of formula HO - R4 - OH is a straight chain alkylene glycol. 